This invention relates generally to gas turbine engines and more particularly to exhaust duct liner attachment systems and methods. In gas turbine engines, it is necessary to protect exhaust ducts with an insulating shield in order to prevent heated core gases from damaging the exhaust ducts. Typically, exhaust ducts are made from titanium-based alloys and have temperature limits of approximately 300° F.-800° F. (˜148.9° C.-426.7° C.). Exhaust gases, however, may reach much higher temperatures, particularly if thrust augmentation is conducted. It is, therefore, necessary to line exhaust ducts with a material that is capable of withstanding the peak temperatures of the core gases and that prevents the exhaust duct from reaching its temperature limitations. Exhaust duct liners are typically made from nickel-based alloys, which have temperature limits of approximately 700° F.-1200° F. (˜371.1° C.-648.9° C.). In order to alleviate some of the heat from the exhaust gases imparted to the liner, cooling air is passed between the exhaust duct and liner and is bled through thousands of small cooling holes in the liner. For example, bypass air is routed between the duct and liner in turbofan engines. Thus, the exhaust duct and liner are subjected to different pressure and temperature gradients, which results in differing deflections and expansions of each body.
In order to maintain the desired temperature and pressure profile along the exhaust duct and liner, it is desirable to maintain proper spacing between the exhaust duct and liner. The differing pressures, temperatures and functional requirements of the exhaust duct, however, produce three-dimensional forces between the duct and liner, which tend to shift the liner out of alignment. Various designs have been put forth to maintain proper alignment, such as described in U.S. Pat. Nos. 7,581,399 and 7,861,535, which are assigned to United Technologies Corporation. Some of these designs, however, require careful insertion of support members through holes in either the exhaust duct or liner. There is, therefore, a need for an easy to install exhaust duct liner suspension system that maintains proper spacing between an exhaust duct and a duct liner, while also permitting the liner to shift in other directions to accommodate, among other things, thermal growth.